Bipolar chargers are used to provide a steady-state electric charge distribution to an aerosol. This is useful for a variety of tasks, including collection, analysis, and measurement of particles in an aerosol.
Aerosols may include charged particles, but the distribution of charges on the particles varies depending on a number of factors. For many applications, particularly for measurement applications, it is desirable to treat, or charge-condition, an aerosol such that it acquires a steady-state electric charge distribution. A bipolar charger may be used to provide such a steady-state electric charge distribution. Certain bipolar chargers operate by providing a mixture of positive and negative ions. This mixture of positive and negative ions is mixed with the aerosol resulting in bipolar diffusion charging. If the ion populations are initially balanced, the charge state of their aerosol will eventually reach a quasi-steady state.
Most bipolar chargers use a radioactive source, which leads to regulatory and transportation issues. This is a major obstacle in conducting field measurements of aerosols using instruments that utilize such radioactive sources. As such, there is a need for a bipolar charger that does not include a radioactive source, is capable of being miniaturized, and is low in cost.